| Message ID | 20240923103406.2509906-1-steven.price@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/panthor: Fix race when converting group handle to group object | expand |
On Mon, 23 Sep 2024 11:34:06 +0100 Steven Price <steven.price@arm.com> wrote: > XArray provides it's own internal lock which protects the internal array > when entries are being simultaneously added and removed. However there > is still a race between retrieving the pointer from the XArray and > incrementing the reference count. > > To avoid this race simply hold the internal XArray lock when > incrementing the reference count, this ensures there cannot be a racing > call to xa_erase(). > > Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block") > Signed-off-by: Steven Price <steven.price@arm.com> Uh, nice catch! Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> > --- > drivers/gpu/drm/panthor/panthor_sched.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > index 42afdf0ddb7e..0dbeebcf23b4 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.c > +++ b/drivers/gpu/drm/panthor/panthor_sched.c > @@ -3242,6 +3242,18 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle) > return 0; > } > > +static struct panthor_group *group_from_handle(struct panthor_group_pool *pool, > + u32 group_handle) > +{ > + struct panthor_group *group; > + > + xa_lock(&pool->xa); > + group = group_get(xa_load(&pool->xa, group_handle)); > + xa_unlock(&pool->xa); > + > + return group; > +} > + > int panthor_group_get_state(struct panthor_file *pfile, > struct drm_panthor_group_get_state *get_state) > { > @@ -3253,7 +3265,7 @@ int panthor_group_get_state(struct panthor_file *pfile, > if (get_state->pad) > return -EINVAL; > > - group = group_get(xa_load(&gpool->xa, get_state->group_handle)); > + group = group_from_handle(gpool, get_state->group_handle); > if (!group) > return -EINVAL; > > @@ -3384,7 +3396,7 @@ panthor_job_create(struct panthor_file *pfile, > job->call_info.latest_flush = qsubmit->latest_flush; > INIT_LIST_HEAD(&job->node); > > - job->group = group_get(xa_load(&gpool->xa, group_handle)); > + job->group = group_from_handle(gpool, group_handle); > if (!job->group) { > ret = -EINVAL; > goto err_put_job;
On Mon, Sep 23, 2024 at 11:34:06AM +0100, Steven Price wrote: > XArray provides it's own internal lock which protects the internal array > when entries are being simultaneously added and removed. However there > is still a race between retrieving the pointer from the XArray and > incrementing the reference count. > > To avoid this race simply hold the internal XArray lock when > incrementing the reference count, this ensures there cannot be a racing > call to xa_erase(). > > Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block") > Signed-off-by: Steven Price <steven.price@arm.com> Reviewed-by: Liviu Dudau <liviu.dudau@arm.com> Best regards, Liviu > --- > drivers/gpu/drm/panthor/panthor_sched.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c > index 42afdf0ddb7e..0dbeebcf23b4 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.c > +++ b/drivers/gpu/drm/panthor/panthor_sched.c > @@ -3242,6 +3242,18 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle) > return 0; > } > > +static struct panthor_group *group_from_handle(struct panthor_group_pool *pool, > + u32 group_handle) > +{ > + struct panthor_group *group; > + > + xa_lock(&pool->xa); > + group = group_get(xa_load(&pool->xa, group_handle)); > + xa_unlock(&pool->xa); > + > + return group; > +} > + > int panthor_group_get_state(struct panthor_file *pfile, > struct drm_panthor_group_get_state *get_state) > { > @@ -3253,7 +3265,7 @@ int panthor_group_get_state(struct panthor_file *pfile, > if (get_state->pad) > return -EINVAL; > > - group = group_get(xa_load(&gpool->xa, get_state->group_handle)); > + group = group_from_handle(gpool, get_state->group_handle); > if (!group) > return -EINVAL; > > @@ -3384,7 +3396,7 @@ panthor_job_create(struct panthor_file *pfile, > job->call_info.latest_flush = qsubmit->latest_flush; > INIT_LIST_HEAD(&job->node); > > - job->group = group_get(xa_load(&gpool->xa, group_handle)); > + job->group = group_from_handle(gpool, group_handle); > if (!job->group) { > ret = -EINVAL; > goto err_put_job; > -- > 2.39.5 >
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c index 42afdf0ddb7e..0dbeebcf23b4 100644 --- a/drivers/gpu/drm/panthor/panthor_sched.c +++ b/drivers/gpu/drm/panthor/panthor_sched.c @@ -3242,6 +3242,18 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle) return 0; } +static struct panthor_group *group_from_handle(struct panthor_group_pool *pool, + u32 group_handle) +{ + struct panthor_group *group; + + xa_lock(&pool->xa); + group = group_get(xa_load(&pool->xa, group_handle)); + xa_unlock(&pool->xa); + + return group; +} + int panthor_group_get_state(struct panthor_file *pfile, struct drm_panthor_group_get_state *get_state) { @@ -3253,7 +3265,7 @@ int panthor_group_get_state(struct panthor_file *pfile, if (get_state->pad) return -EINVAL; - group = group_get(xa_load(&gpool->xa, get_state->group_handle)); + group = group_from_handle(gpool, get_state->group_handle); if (!group) return -EINVAL; @@ -3384,7 +3396,7 @@ panthor_job_create(struct panthor_file *pfile, job->call_info.latest_flush = qsubmit->latest_flush; INIT_LIST_HEAD(&job->node); - job->group = group_get(xa_load(&gpool->xa, group_handle)); + job->group = group_from_handle(gpool, group_handle); if (!job->group) { ret = -EINVAL; goto err_put_job;
XArray provides it's own internal lock which protects the internal array when entries are being simultaneously added and removed. However there is still a race between retrieving the pointer from the XArray and incrementing the reference count. To avoid this race simply hold the internal XArray lock when incrementing the reference count, this ensures there cannot be a racing call to xa_erase(). Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block") Signed-off-by: Steven Price <steven.price@arm.com> --- drivers/gpu/drm/panthor/panthor_sched.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)